Photoelectric organ



July 7, 1964 R. E. WILLIAMS PHOTOELECTRIC ORGAN Filed Feb. 3, 1960 2Sheets-Sheet 2 HIE-.8

BY Y veqe/ ATTORNEYS 3,140,337 PHOTOELECTRIC ORGAN Richard E. Williams,Fairfax, Va., assignor to Scope, Inc., Fairfax, Va., a corporation ofNew Hampshire Filed Feb. 3, 1960, Ser. No. 10,829 3 Claims. (Cl.84--1.18)

This application is a continuation-in-part of my application for US.patent, Serial No. 753,354, filed August 5, 1958, and entiledPhotoelectric Organ.

The present invention relates generally to electronic musicalinstruments, and particularly to electronic musical instruments whichemploy photo-electric tone generators.

In principle, photo-electric musical instruments generate tones byutilizing recorded tone or pitch patterns to modulate light passing toone or more photo-electric cells. The tone or pitch patterns may be ofvariable density or variable area type, and the techniques involved arein some respects similar to those employed in recording and reproducingsound on film. A large number of systems have been conceived in the pastfor generating photoelectrically the large number of tones required incommercial electronic musical devices, and a wide variety of techniqueshave been developed for this purpose. For example, pitch or tone discshave been employed. Such discs are usually entirely clear or translucentexcept for the presence of a large number of opaque waveform patternsexisting in concentric bands on the disc. If a narrow beam of light isfocused on one of these bands as the disc rotates, and if aphotoelectric tube is placed on the other side of the disc to interceptthe light, light passing through the bands is modulated by thevariations of opacity of the band, and the amount of light reach ing thephoto-electric tube varies in accordance with the area of clear bandbetween the light source and the photoelectric tube. Accordingly, thephototube output current varies in exact accord with the shape of theopaque waveform pattern. If the disc is turned at a sufliciently rapidrate so that the variations of photo-electric tube current occur at anaudio rate, the output current from the tube may be amplified andacoustically radiated. Key controlled systems may be provided forselectively illuminating several bands or pitch tracks, so that bysuitably manipulating the keys musical selections may be generated.

The problem then arises of making the pitch tracks re-entrant, i.e.,inscribing or recording on the pitch disc tracks wherein the totalnumber of cycles per track is so related to the length of the track thatan integral number of cycles is recorded on each track. This isextremely diflicult of accomplishment because the ratio between adjacentfrequencies in the tempered scale varies as the twelfth root of two, andbecause the accuracy with which frequency must be reproduced inelectronic musical instruments is better than .25% for the average humanear, and is approximately .1% for the trained musical ear.

In order to generate re-entrant pitch tracks which have the requiredfrequencies it had heretofore been found essential either to utilize avery low speed disc with extremely long tracks, which leads to discs ofunreasonable size, or to utilize separate discs for tones of differentno- I menclature. It might appear that a relatively small disc couldcontain a large number of tracks provided a sufficiently large number ofcycles of approximately correct United States Patent 3,140,331 PatentedJuly 7, 1964 ice frequencies were recorded on each track, and that thetracks may be then made re-entrant without appreciable error in tonefrequency. This turns out to be an inadequate solution, because theproblem is then introduced of illuminating the tracks with a beam oflight which is sufficiently narrow in the direction of track length thata very small fraction of a cycle is illuminated at any given instant oftime, and yet to provide, sutlicient light at the photoelectric cell torise above the noise level of the circuitry involved. This proves to beimpossible unless a small number of cycles of tone per track isemployed, and this difiiculty is sometimes described as resulting from alow light storage index.

Still a further problem relates to the speed at which the disc may berotated. If the disc is rotated with sufficient slowness, and therelatively small light storage index is somehow accommodated, arelatively large number of tone cycles per track may be employed.However, when this is attempted problems of controlling and renderinguniform the rotation of the tone disc exist because of the extremely lowmomentum of the mechanical system. Any slight inaccuracies ornon-uniformities of pitch track rotation rate become accentuatedaudibly, and in practice this approach has been proven to be totallyunsuccessful.

The usual solution attempted has been to provide plural tone discs, onefor each note of a given nomenclature, and to gear these tone discstogether so that they rotate at the appropriate speeds. Thereby eachtone disc must be associated with a photocell, and since there aretwelve notes of dilferent nomenclature in the evenly tempered scale,twelve discs and twelve photocells are required, in addition toappropriate gearing systems. The system then becomes cumbersome andexpensive to build and is believed to be commercially impractical.

The present invention provides a musical instrument which utilizes sixpitch discs, which are driven in pairs so that only three difierentspeeds are required. Each disc employs a total of ten tracks,representing tones of two ditferent but adjacent nomenclatures, in fiveoctaves for each nomenclature. For example, we may denote discs of thesame rotary speed as A and B discs, respectively, and disc pairs ofdifferent speeds as #1, #2 and #3 discs. The speeds employed are 5.46,6.88 and 8.66 r.p.s., which represent vibrato frequencies, orfrequencies in the vibrato range. The tracks for these speeds mayrepresent recorded tones as follows:

Speed Disc A Disc B Tone Tone 5.46 r.p.s F, Fit G, Gt; 6.88 r.p.s A, AlfB, C 8.66 r.p.s Cit, D D3, E

The recorded number of cycles per track corresponding with these tonesare:

It is then apparent that all the A discs are duplicates and all the Bdiscs are duplicates, so that a total of only two different discs isrequired, and that the total number of wave length representations pertrack is small, enabling convenient utilization of, say, three inchdiscs with adequate high light storage factors. Since the number ofcycles is always integer, i.e., n16, n17, n18, 1119, where n is aninteger representing the octave, the re-entrance problem isnon-existent, and it is found that no generated tone is inaccurate bymore than 2%.

It will be clear as the description proceeds that the principles of theinvention may be applied to magnetic recording systems, in which pitchtracks on magnetic tape or drums are reproduced, as well as tophotoelectric systems. For purposes of illustration of the principles ofthe invention in its broadest aspects, and further to indicate how apreferred form of the invention may be practiced, the system isdescribed as photoelectric.

Rotation of the discs at different speeds, all within the vibrato range,has the effect of introducing variety into the reproduced tone, whenplying chords, which is parthe spoilage factor in tone track synthesisand disc duplication to negligible factors.

' In accordance with the present invention the discs may be rotated by agood quality motor, and, without more, adequate speed regulation of thediscs is attained since any variations of speed during a cycle due toslight frequency misregulation of the motorpower source do not produceunpleasant effects on the listener.

A further problem which exists in the production of photoelectric organsrelates to the complexity of the optical system employed. Many systemswhich have been conceived in the past employ relatively long lightpaths, or complex lenses, or reflectors. These may readily becomemaladjusted and in adidtion are relatively expensive to fabricate. Theproblem of selecting tone track in a tone wheel having a great number oftracks without introducing optical or mechanical complexity is one ofthe serious problems which has heretofore prevented the development of apractical photoelectric organ. Not only may the tracks be quite narrow,but the distance between tracks may be still narrower. The total amountof light falling on each track must be approximately the same as for anyother track, or different notes will have different amplitudes whenacoustically transduced. It is necessary that the light beams relatingto each track remain relatively symmetrical with respect to the track asthe track rotates. It is further necessary that if the beams diverge incross-sectional area after leaving the track and on the way to thephotocell, approximately the same area of the photocell will beilluminated by all the tracks, since otherwise again different noteswill have different acoustic amplitudes.

In accordance with the present invention the tracks are selected bymeans of light bulbs individual to the tracks. In order to illuminateeach track an energizing circuit is provided to energize a specificlight bulb associated with that track. The light bulbs are mounted on aplane plate behind slits. They are adjustably mounted so that smallmechanical motions of the bulb will be permitted for purposes ofadjustment. Positions of the slits and the sizes of the slots relativeto the position of the bulb are so selected that light from any givenbulb can proceed via only one slot and via one track to the photocell.Adjustment of a light bulb with respect to its slit permits adjustmentof the amount of light transferred from the bulb to the photocell andalso permits adjustment of the overlie of the light beam on its trackand the extent to which the light beam illuminates the cathode of thephotocell. It is a simple matter to energize the bulb and thereafter tomove same slightly on its adjustable mounting until only a single trackgenerates the tone, and until that tone is of required loudness. It hasbeen found feasi ble in accordance with the principles of the presentinvention to utilize sixty tracks on six discs, to associate one hundredand twenty different lamps with the sixty tracks (i.e., two lamps pertrack), and to derive undistorted tone from any one of the tracks byilluminating the corresponding lamp, and this with a minimum ofmechanical complexity, by means of a structure which lends itself toeconomical fabrication, to ease of maintenance and to freedom frommaintenance requirements as well as to ease of adjustment of the systemduring manufacture or thereafter, in respect to obtaining pure tones ofdesired amplitudes. The system, while accomplishing these objectivesrequires no lenses and no reflectors in the optical system.

Some assistance in providing pure tones without intermodulation betweentracks is accomplished by the method adopted for grouping the sound orpitch tracks on the disc. In accordance with the present invention pitchtracks of the same nomenclature are immediately adjacent each other.Between groups of tone tracks relating to a given nomenclature arelatively large space is left, following which appear tones of anothernomenclature. In this way, if there is some intermodulation by reason ofthe fact that light from one bulb impinges totally on one track and tosome degree on an adjacent track, intermodulation is harmonic in natureand, therefore, is not unpleasant and does not detract from the musicalquality of the instrument.

According to another feature of the present invention, the photocellsemployed in the track reading system are off-centered with respect tothe disc, whereby two photocells may be employed which are independentlyilluminated by separate sets of lights, but via the same sound tracks.Accordingly, each sound track is doubly employed. This expedient is ofparticular value in two manual organs, for example, in which case thesame sound track may be employed for generating sounds relating to bothmanuals, but each manual may utilize a different set of lights an adifferent photocell. Maximum manuals utilized in organs of conventionalcharacter employ sixty keys. Accordingly, by means of this expedient itis possible to employ one-hundred and twenty lamps, sixty per manual,and two photocells, by means of which the separate manuals may becompletely independent of one another except for the duplicate use oftracks. In the two manually system, the separate photoelectric cells areconnected to separate pre-amplifiers and separate sets of formantfilters, the outputs of which are applied directly to a power amplifierand a transducer. A variety of modifications of the basic organ may beemployed: For example, keys may be interlocked, so that when a key of agiven nomenclature is depressed, the key of corresponding nomenclaturebut an octave higher may also be depressed, thereby enriching thegenerated tone. On the other other hand a given tone may be coupled inthis way to a tone which is an octave below or above the primarilydesired tone. This is equivalent in organ terminology to coupling in afour foot or sixteen foot rank to an eight foot rank.

According to a further feature of the invention, correction is made forthe fact that each light bulb is at a different distance from itsassociated track and from its associated photocell. This fact, taken inconjunction with the further fact that light diminishes in intensity asa function of distance from its source according to a square law, leadsto certain difliculties. The intensty of light falling on any track maybe different from the intensity of light falling on other tracks, andthe decrease in both intensity of light and in divergence of light bedifferent for each track. The dilficulty is increased by virtue of thelocations of the several tracks radially,

as a function of pitch, i.e., adjacent tracks do not represent adjacentpitches, but represent octavally separated pitches. The difference inlight intensity for pitches of adjacent octaves may therefore, beslight, but the difference for adjacent pitches may be considerable andquite noticeable. These differences are compensated by adjusting lamppositions to increase or decrease the amount of light reaching each cellfrom each lamp.

It is, accordingly, a broad object of the present invention to provide anovel electronic musical instrument.

It is a further object of the present invention to provide a novelmusical instrument of the electronic organ type.

Still another object of the invention resides in the provision of aphotoelectric organ employing only two distinct types of tone disc forgenerating a complete complement of organ tones.

Still another object of the invention resides in the provision of aphotoelectric organ which employs no lenses or reflectors. i

A further object of the invention resides in the provision of a singlemechanically simple assemblage for interrelating tones discs, lightsources, photoelectric cells and light apertures in a small, compact,light unit having no reflectors and no lenses and which permitsselection of any tone track at will.

Another object of the invention is the provision of a multiple pitchdisc for a photoelectric organ in. which the discs are rotated atdifferent frequencies falling within the vibrato range.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of one specific embodiment thereof,especially when taken in conjunction with the accompanying drawings,wherein:

FIGURE 1 is a schematic circuit diagram of a photoelectric organaccording to the present invention;

FIGURE 2 is a partial view in perspective of a photo electric toneread-out system, according to the present invention;

FIGURE 3 is a partial view in plan of a tone disc according to theinvention, and

FIGURE 4 is a view in perspective of a drive mechanism for the pluraltone discs of the invention.

The several tone discs of the present invention may be fabricatedaccording to the general method disclosed in my co-pending applicationSerial No. 753,354, entitled Photoelectric Organ, and filed August 5,1958, making such quantitative modifications as are required by the discspeeds and tone tracks of the present invention, specified herein.

Reference is made to FIGURE 3 of the accompanying drawings, wherein isillustrated a portion of a pitch disc 10, as finally recorded anddeveloped. Two sets of tracks 11. and 12 are illustrated, each setcomprising five octavally related tracks of a given nomenclature, andthe two sets being adjacent in nomenclature. Six discs are utilized, toprovide for twelve nomenclatures. Of the six discs, half are designatedA discs and half B discs. The A discs each contain five tracks rooted on16'wave length representations and five tracks rooted on 17 wave lengthrepresentations, but separate ones ofthe A discs are rotated atdifferent speeds, i.e., 5.46 r.p.s., 6.88' r.p.s., and 8.66 r.p.s. The Bdiscs contain eachfive tracksrooted on 18 wave length representationsand five tracks rooted on 19 wave length representations, and arerespectively rotated at the same speeds as the A discs, in pairs. Accordingly, one A and one B disc rotate at 5.46 r.p.s.,

one A disc and one B disc at 6.88 r.p.s. and one A disc and one B discat 8.66 r.p.s.

The A disc, rotating at 5.46 r.p.s., has recorded thereon all toneshaving the nomenclatures F, Fit, and the B disc rotating at 5.46 r.p.s.all tones having the nomen- Speed Tone Tone Disc A Disc B F Flt G, G4;A: Alt B, o tt. D 5. E

The tracks are accordingly all re-entrant, because based on integers,and yet only two different pitch discs are utilized. The tracks 11 and12 of the same nomenclature are closely spaced radially, but aconsiderable radial gap 13 subsists between the set of tracks 11 and theset of tracks 12. Thereby, if read-out occurs with some inaccuracy ofany single tone track, only octavally related frequencies can beinadvertently introduced, but not tones of adjacent nomenclature.

The mode of driving the tone discs is illustrated in FIGURE 4 of theaccompanying drawings, wherein 15 is a synchronous electric motor,suitably geared down, and which rotates a central drive disc 16, securedon the shaft of motor 15. The central drive disc 16 frictionally drivesthree driven discs 17, 18, 19, at the peripheries of the respectivediscs, and the ratios of the disc diameter of the latter are selected toprovide the required driven disc speeds, i.e., 5.46 r.p.s., 6.88 r.p.s.,and 8.66 r.p.s., respectively, for the several discs 17, 18 and 19.

The several pitch disc pairs are secured to shafts common to the drivendiscs 17, 18, 19 and the angular separations of the driven discs 17, 18,19 is Proceeding to FIGURES l and 2 of the accompanying drawings, atypical driven disc 17 is illustrated, having a shaft 20. On the shaft20 are two tone discs, 21, 22, i.e., one A disc and one B disc, forrotation with driven disc 17. Located between the tone discs 21, 22adjacent their peripheries, are four photoelectric cells 23, 24, 25, 26.The photoelectric cells 23, 25 pertain to and face the pitch disc 22,and the photoelectric cells 24, 26 pertain to and face the pitch disc21.

A plurality of lamps is provided, there being specifically one lamp foreach key of a first manual of an organ, and one lamp for each key of asecond manual of an organ, in a two manual organ.

Lamps pertaining to the first manual, i.e., manual A are designated bythe reference numeral 61 while those pertaining to the second manual,i.e., manual B are designated by the reference numeral 62. Each of thelamps includes a filament and specifically a line filament, the filamentbeing aligned with the radii of the pitch discs. The lamps 61 arearranged in the area circumscribed by a semi-circle having a diameterpassing through the shaft 20. Similarly, the lamps 62 are located withinthe area defined by a further semi-circle having the same diameter. Eachof the lamps is associated with a narrow radially elongated slit, as 63,in a slit plate SP. Each slit, and. the associated lamp are so locatedwith respect to an associated pitch track, as 65, of a pitch disc, as22, that light from the lamp passes through a slit 64 and thence throughthe required pitch track, as 65, and the'nce to a photocell as 24 or 25.The A manuallamps 61 are associated with photocell 23, and illuminateonly that photocell, while the B manual lamps are associated with aseparate photocell 25, and illuminate only the latter.

In general, each separate lamp as 61 or 62 is associated with a singletrack, but the tracks serve a double function, in that one lamp of the Amanual'lamps 61 and one lamp of the B manual lamps 62 are associatedwith each one of the tracks 65. It follows that the photocells 23, and24 may provide identical tonal outputs, i.e., of the same nomenclatureand scale position, when suitable 'keys in the two manuals aredepressed, but these identical tonal outputs are provided via separatephotocell output one of lamps 61, 62 is energized. In FIGURE 1 oftheaccompanying drawings, I have illustrated three keys 70,. 71, 72,taken from manual A and three keys taken from manual B. It will beobserved that the manual A keys 70, 71 and 72 connect separate ones ofthe lamps of the A group to a source of voltage, while the key actuatedswitches 73, 74 and 75 pertaining to the B manual, control the lamps ofthe B group. All the lamps, nevertheless, may be energized from the samesource B, or, if desired, lamps pertaining to the separate manuals maybe provided with separate power supplies. Electrical signals generatedby the photocell 23 in response to tone modulated light originated byany of the lamps 61 pertaining to manual A are supplied via lead 80 to apre-amplifier 81, which pertains to manual A only. Similarly, the outputof photocell 25 is applied via a lead 82 to a preamplifier 83 whichpertains to the B manual only. The

output of the pre-amplifier A is passed through a group of formantfilters 84 which pertains to the manual A, and separate filters of whichare selected by means of the stop switches 85. Similarly, the output ofpre-amplifier B is applied to a group of formant filters 87 which areselected by means of stop switches 88. The outputs of the formantfilters 84, 87 are combined in a resistance 90 which includes anadjustable slider 91 acting as a volume control for the system.

The combined outputs on the slider 91 are applied to a power amplifier92 and thence to an acoustical radiator 93, such as a loudspeaker. Tothe amplifier 92 is also supplied vibrato modulation deriving frommodulator 94, which modulates the frequency of output of the amplifier92 at a vibrator rate suitable to the system. It is important to notethat the vibrato rate employed can no longer be equal to the rate ofrotation of all the pitch discs, since the latter are not identical. Inmy prior ap plication, hereinabove referred to, the vibrato rateemployed was equal to the rate of rotation of the single disc employed.In accordance with the present invention,

any variation of speed of the pitch discs results in interjitter in thepitch discs is translated into a vibrator effect which is pleasant tothe ear.

In the system of FIGURES 1 and 2, since generation of the tonesappropriate to any single manual require the utilization of six pitchdiscs and since each manual includes circuitry for reading out eachpitch disc, which in turn includes a photocell, all six photocellspertaining to a manual are connected in parallel, as indicated generallyin FIGURES l or 2 of the photocells.

An important structural feature according to the present inventionresides in the location of the photocells as 23, 24 pertaining to onepair of A and B pitch discs, at locations intermediate the pitch discs.The slit discs 64 then are located outside the pitch discs and the lampmounting plates and lamps are located outside the slit plates, asillustrated in FIGURE 2. Electrically considered, then, the signalspertaining to any one manual are identical to signals which might beprovided were a single photocell and single pitch disc utilized. Theymay, therefore, be processed in the manner specified and described indetail in my above referred to application for US. patent. Similarly,the total number of lamps employed in the two systems,'i.e., the presentsystem and the system of my above identified application for US. patent,may be identical. And accordingly the circuitry utilized forcontrollably energizing the lamps may be identical in the two systems,and the circuit expedients therein described and illustrated in detailare incorporated herein by reference.

In place of a pair of lamps connected in parallel, as 23, 24, I may alsoutilize a single photocell associated with two mirrors, which reflectlight deriving from the lamps via the tone tracks to the cell. Also, asingle cell, as 23, may be employed, the remaining cell of a pair, as24, being replaced by a mirror which directs light to the cell 23.

While I have described and illustrated one specific embodiment of myinvention, it will be clear that variations of the details ofconstruction which are specifically illus trated and described may beresorted to Without departing from the true spirit and scope of theinvention as defined in the appended claims.

What I claim is:

1. A tone disc assembly, comprising a first and second rotatablevariable translucency tone disc, each of said tone discs includingopaque areas representing a plurality of tone tracks of differentnomenclature, an aperture plate operatively associated with each of saidtone discs, said tone discs located between said aperture plates, saidaperture plates each including at least one aperture operativelyassociated with each of said tone tracks, a plurality of discretesources of light, each of said sources of light being located adjacentone of said apertures, photoelectric cells, said cells, apertures,tracks and discrete sources of light being relatively so located thatlight from each source of light travels to one of said photoelectriccells via one only of said apertures and one only of said tracks in theorder stated, wherein said tone discs are concurrently driven by asingle shaft, one of said tone discs having only tracks representing atleast five octaves of tones of each of a first and second nomenclature,the other of said tone discs having only tracks representing at leastfive octaves of tones of each of a third and fourth nomenclature, saidfour tones being in immediate succession in the musical scale and eachtone track being recorded in an integral number of wave lengthrepresentations, tracks representing tones of each single nomenclatureon each of said tone discs being located in a group in close proximityto one another, and separate groups being relatively widely separated onsaid tone discs, and means for selectively reading out said tracks, saidmeans including key switch means for selectively activating said sourcesof light to selectively illuminate said tracks.

2. A musical instrument, comprising a pair of tone discs on a singleshaft, one of said tone discs having only tracks representing at leastfive octaves of tones of each of a first and second nomenclature, theother of said tone discs having only tracks representing at least fiveoctaves of tones of each of a third and fourth nomenclature, said fourtones being immediately successive in the musical scale and each tonetrack being recorded in an integral number of wave lengthrepresentations, an aperture plate operatively associated with each ofsaid tone discs, said tone discs located between said aperture plates,said aperture plates each including at least one aperture operativelyassociated with each of said tone tracks, a plurality of discretesources of light, each of said sources of light being located adjacentone of said apertures, photoelectric cells, said cells, apertures,tracks and discrete sources of light being relatively so located thatlight from each source of light travels to one of said photoelectriccells via one only of said apertures and one only of said tracks in theorder stated.

3. A system for producing music from photographically recorded tonetracks, comprising a re-entrant disc record carrying medium, said mediumhaving three disc pairs moving at different speeds related in the ratio5.46, 6.88 and 8.66, and carrying tone tracks having only l6n, 17n,

9 18n and 19n complete cycles of tone, where n are integers including 1,2, 3 denoting order of octaves of said tone in the tonal range of thesystem, an aperture plate operatively associated with each of said tonediscs, said tone discs located between said aperture plates, saidaperture plates each including at least one aperture operativelyassociated with each of said tone tracks, a plurality of discretesources of light, each of said sources of light being located adjacentone of said apertures, photoelectric cells, said cells, apentures,tracks and discrete sources of light being relatively so located thatlight from each source of light travels to one of said photoelectriccells via one only of said apertures and one only of said tracks in theorder stated.

References Cited in the file of this patent UNITED STATES PATENTS1,167,663 Sinclair et a1. Jan. 11, 1916 2,038,976 Wood et al Apr. 28,1936 2,164,809 Fisher July 4, 1939 2,243,090 Dudley May 27, 19412,469,850 Spielrnan May 10, 1949 2,754,713 Bajolet July 17, 19502,941,434 Clark July 21, 1960 2,946,253 Clark July 26, 1960

1. A TONE DISC ASSEMBLY, COMPRISING A FIRST AND SECOND ROTATABLE VARIABLE TRANSLUCENCY TONE DISC, EACH OF SAID TONE DISCS INCLUDING OPAQUE AREAS REPRESENTING A PLURALITY OF TONE TRACKS OF DIFFERENT NOMENCLATURE, AN APERTURE PLATE OPERATIVELY ASSOCIATED WITH EACH OF SAID TONE DISCS, SAID TONE DISCS LOCATED BETWEEN SAID APERTURE PLATES, SAID APERTURE PLATES EACH INCLUDING AT LEAST ONE APERTURE OPERATIVELY ASSOCIATED WITH EACH OF SAID TONE TRACKS, A PLURALITY OF DISCRETE SOURCES OF LIGHT, EACH OF SAID SOURCES OF LIGHT BEING LOCATED ADJACENT ONE OF SAID APERTURES, PHOTOELECTRIC CELLS, SAID CELLS, APERTURES, TRACKS AND DISCRETE SOURCES OF LIGHT BEING RELATIVELY SO LOCATED THAT LIGHT FROM EACH SOURCE OF LIGHT TRAVELS TO ONE OF SAID PHOTOELECTRIC CELLS VIA ONE ONLY OF SAID APERTURES AND ONE ONLY OF SAID TRACKS IN THE ORDER STATED, WHEREIN SAID TONE DISCS ARE CONCURRENTLY DRIVEN BY A SINGLE SHAFT, ONE OF SAID TONE DISCS HAVING ONLY TRACKS REPRESENTING AT LEAST FIVE OCTAVES OF TONES OF EACH OF A FIRST AND SECOND NOMENCLATURE, THE OTHER OF SAID TONE DISCS HAVING ONLY TRACKS REPRESENTING AT LEAST FIVE OCTAVES OF TONES OF EACH OF A THIRD AND FOURTH NOMENCLATURE, SAID FOUR TONES BEING IN IMMEDIATE SUCCESSION IN THE MUSICAL SCALE AND EACH TONE TRACK BEING RECORDED IN AN INTEGRAL NUMBER OF WAVE LENGTH REPRESENTATIONS, TRACKS REPRESENTING TONES OF EACH SINGLE NOMENCLATURE ON EACH OF SAID TONE DISCS BEING LOCATED IN A GROUP IN CLOSE PROXIMITY TO ONE ANOTHER, AND SEPARATE GROUPS BEING RELATIVELY WIDELY SEPARATED ON SAID TONE DISCS, AND MEANS FOR SELECTIVELY READING OUT SAID TRACKS, SAID MEANS INCLUDING KEY SWITCH MEANS FOR SELECTIVELY ACTIVATING SAID SOURCES OF LIGHT TO SELECTIVELY ILLUMINATE SAID TRACKS. 